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fix memory leak in {host,device}_vector::reserve #1447
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Inside of append(), for the case that the underlying storage had to be reallocated to accomodate its new capacity, the code is currently using the old storage (ie., `m_storage`) to do the default construction, and possibly destruction when needing to clean up after an exception. It is more consistent to use the `new_storage` member functions to do so -- after all we are constructing (or destroying) elements in that `new_storage` here. This is essentially a cleanup only, it doesn't actually change behavior, since `new_storage` is created to use a copy of the allocator that's in `m_storage`, so the `default_construct_n` and `destroy` functions called are identical in practice -- it just makes this piece of code more consistent.
Currently, when using reserve() to actually grow the storage in a vector, a new backend storage is allocated, but the old one is never deallocated. A more minor unexpected behavior that also occurred is that the vector would still apply its exponential growth behavior, ie., it when taking a vector of size 3 and calling `.reserve(4)` on it, one would actually end up with a vector of size 6. The logic to allocate the new storage, copy in the existing elements, then destroy the old elements and swap in the new storage (which does to the old storage being destructed and hence deallocated) is, essentially, taken from how `.resize()` works. When growing a vector using `.reserve()`, the new capacity will now be exactly what was specified in the call to `.reserve()`.
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Can one of the admins verify this patch? |
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Thanks Kai, this looks good to me. I'll start testing and target this for 1.13. run tests |
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DVS CL: 30027183 |
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Jun 8, 2021
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This fixes #1443 --
.reserve()did not actually deallocate the memory previously allocated when allocating a new, larger storage area. It also disables the capacity growing exponentially when using.reserve(), instead the vector will be grown exactly to the capacity specified, as is the case forstd::vector.See commit messages for some more detail.